All-inorganic high-temperature-resistant composite magnetic powder core and preparation method thereof
Technical Field
The invention relates to the technical field of magnetic components, in particular to an all-inorganic high-temperature-resistant composite magnetic powder core and a preparation method thereof.
Background
The sendust/sendust magnetic powder core is widely applied to the fields of communication, uninterruptible power supplies, solid laser power supplies, photovoltaic power generation systems and the like because of high saturation magnetic induction intensity and relatively low loss. The sendust/sendust material has power loss in an alternating magnetic field and is dominated by eddy current loss at high frequency. The eddy current among the particles can be blocked by insulating and coating the magnetic powder particles, and the eddy current loss of the magnetic powder core is reduced, so that the iron-silicon-aluminum/iron-silicon magnetic powder core with high magnetic conductivity and low loss is obtained.
The use of organic polymers as insulating agents and binders has been commercialized. The organic resin is adopted to coat the magnetic powder particles, so that the resistivity of the powder core can be obviously improved, and the loss of the magnetic powder core can be reduced. More importantly, the organic polymer has poor high temperature resistance, the general heat-resistant temperature is not more than 500 ℃, and the conventional heat treatment temperature can reach 600-800 ℃.
In recent years, inorganic insulating agents such as phosphates and ceramic oxide coatings have received much attention and have been under some progress. However, the chemical stability and structural stability of the phosphated coating are poor, and as the annealing temperature increases, the coating insulation decreases, resulting in increased losses. When ceramic oxide is adopted for coating, the material can withstand higher heat treatment temperature, but the adhesion between the oxide coating layer and the powder core is poor, so that good insulating coating is difficult to form on the surface of the powder core, meanwhile, the thickness of the oxide coating layer is difficult to control, the thickness of the insulating coating layer is difficult to control on a nanometer scale, and along with the increase of the thickness of the insulating coating material, the air gap rate inside the powder core is increased, so that the magnetic permeability of the magnetic powder core can be reduced. More importantly, the excessive oxide coating can lead to uneven insulation coating, the powder core is easy to crack in the compression molding process, and the eddy current loss of the magnetic core is increased. Therefore, how to select a proper all-inorganic coating material and a proper coating thickness is a great challenge to realize a high-permeability and low-loss powder core.
Chinese patent literature discloses a ferrite composite magnetic powder core and a preparation method thereof, the application publication number of which is CN103426584A, and the invention adopts nickel-zinc ferrite nano particles prepared by a hydrothermal method to coat magnetic powder to prepare the novel nickel-zinc ferrite composite magnetic powder core. However, in this patent, the ferrite and the magnetic powder are in solid-solid contact, so that the wettability is poor, and it is difficult to form a good coating. In addition, the values of permeability and loss of the product are not mentioned in this patent either.
Chinese patent literature discloses an inorganic insulating binder for a metal soft magnetic powder core, the application publication number of which is CN101089108A, the inorganic insulating binder of the invention is made of SiO2、Al2O3、ZrO2Mica powder and water, and has the double effects of insulation and bonding. However, the ceramic oxide and other materials used in the patent are insoluble in water, and it is difficult to obtain an aqueous solution with uniform distribution, so that the uniformity and thickness of the insulating binder coated on the surface of the magnetic powder are difficult to control, the Q value is low, and the loss is increased.
The Chinese patent literature discloses a method for coating and bonding a metal magnetic powder core by using inorganic gel, the application publication number of the method is CN109616273A, the coating agent of the method is one or two of magnesium aluminum silicate, saponite, bentonite and montmorillonite, and the binder is attapulgite. The inorganic gel coating layer is high temperature resistant, and reduces the cost and loss of the magnetic powder core. However, in the patent, because the particle sizes of the magnesium aluminum silicate, the attapulgite and the like are in the micron order, the uniform distribution in the gel is difficult to realize, and the gel has poor fluidity in the magnetic powder and can generate an agglomeration phenomenon. Meanwhile, the gaps between large particles are difficult to fill, so that the magnetic permeability is reduced. Moreover, the metal magnetic powder needs to be passivated and treated, which increases the preparation cost.
Based on the above problems, it is significant to design a new all-inorganic high temperature resistant insulating coating agent to simultaneously realize high magnetic permeability and low loss of the metal magnetic powder core.
Disclosure of Invention
The invention provides a preparation method of an all-inorganic high-temperature-resistant composite magnetic powder core, which aims to solve the problems of uncontrollable coating layer thickness, easy cracking, low magnetic powder core magnetic conductivity, high loss and poor high-temperature resistance of the existing magnetic powder core insulation coating process, and has the advantages of low cost, simple operation and easy large-scale production.
The invention also provides the all-inorganic high-temperature-resistant composite magnetic powder core prepared by the preparation method, and the magnetic powder core has the characteristics of controllable coating thickness, low loss, high magnetic conductivity and high temperature resistance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of an all-inorganic high-temperature-resistant composite magnetic powder core comprises the following steps:
(1) adding FeSiAl metal soft magnetic powder into NaAlO2And (NaPO)3)6Heating and stirring the mixed solution uniformly, and drying to finish insulating coating; NaAlO2And (NaPO)3)6The mixed solution has good fluidity and wettability, and NaAlO is controlled2And (NaPO)3)6The proportion of (A) can be regulated and controlled, and Al (OH) generated by hydrolysis3The FeSiAl soft magnetic powder can be uniformly and compactly coated on the outer surface of the FeSiAl soft magnetic powder; the concentration and the dosage of the mixed solution can be controlled, and the final Al can be controlled on the nanometer scale2O3The thickness of the coating layer effectively prevents the coating layer from cracking, improves the resistivity of the magnetic powder core and reduces the loss;
(2) adding a composite binder into the FeSiAl metal soft magnetic powder subjected to the insulation coating treatment in the step (1), fully stirring, keeping the temperature at 90-100 ℃ for 20-40 min, drying, adding a lubricant, and performing compression molding to obtain a composite magnetic powder core blank; the composite binder is NaOH and Na2SiO3A mixture of (a); using NaOH and Na2SiO3The mixture is used as a composite binder, and the composite binder has good adhesiveness and high temperature resistance, and can prevent the device from losing effect in high-temperature use
(3) And (3) carrying out heat treatment on the composite magnetic powder core blank obtained in the step (2) in vacuum or inert gas or reducing atmosphere, cooling and spraying to obtain the all-inorganic high-temperature-resistant composite magnetic powder core. Al (OH) coated on the outer surface of the FeSiAl metal soft magnetic powder in the heat treatment process3Decomposition to Al2O3Nanoparticles, Al while achieving coating2O3The nanoparticles can be filled in the large particles and the large particles in the magnetic powder coreThe micro-gaps between the particles reduce the gap degree, increase the density of the powder core and obtain higher magnetic conductivity.
Preferably, in the step (1), the NaAlO is based on the total mass of the FeSiAl metal soft magnetic powder2And (NaPO)3)6The mixed solution of (A) comprises 0.05-3 wt% of NaAlO20.01 to 0.08wt% (NaPO)3)6And 10 to 15wt% of water. The final Al can be controlled on the nanometer level by adjusting the concentration and the dosage of the aqueous solution2O3The thickness of the coating layer effectively prevents the coating layer from cracking, improves the resistivity of the magnetic powder core and reduces the loss.
Preferably, the NaAlO2And (NaPO)3)6The mixed solution of (A) comprises 0.1-2 wt% of NaAlO20.02 to 0.05wt% (NaPO)3)6。
NaAlO2And (NaPO)3)6The aqueous solution has good fluidity and wettability by controlling NaAlO2And (NaPO)3)6The hydrolysis reaction can be regulated and controlled. Al (OH) formed by hydrolysis3Can be uniformly and compactly coated outside the magnetic powder core and decomposed into Al in the subsequent thermal annealing treatment process2O3Nanoparticles, Al while achieving coating2O3The nano particles can fill micro gaps between large particles in the magnetic powder core, so that the gap degree is reduced, the density of the powder core is increased, and higher magnetic conductivity is obtained.
Preferably, the heating temperature is 80-100 ℃, and the drying temperature is 90-120 ℃.
Preferably, in the step (2), the composite binder is 0.5-5 wt% of Na based on the total mass of the FeSiAl metal soft magnetic powder2SiO3And 0.002-0.02 wt% of NaOH.
Preferably, the composite binder consists of 1-3 wt% of Na2SiO3And 0.005-0.015 wt% of NaOH. .
Preferably, in the step (2), the lubricant is added in an amount of 0.5 to 1.0 wt% based on the total mass of the FeSiAl metal soft magnetic powder.
Preferably, in the step (2), the lubricant is one or two of zinc stearate and barium stearate.
Preferably, in the step (3), the heat treatment temperature is 600-780 ℃ and the time is 0.5-2 h.
An all-inorganic high-temperature-resistant composite magnetic powder core prepared by the preparation method.
Therefore, the invention has the following beneficial effects:
(1) the coating agent used by the invention is water-soluble, has good fluidity and wettability, and can realize uniform and compact coating of the magnetic powder core, thereby improving the resistivity of the magnetic powder core and reducing the power loss; the preparation method is simple, has low cost and no pollution to the environment, and is suitable for mass production;
(2) the all-inorganic high-temperature-resistant composite magnetic powder core prepared by the preparation method has the characteristics of controllable coating layer thickness, low loss, high magnetic conductivity and high temperature resistance.
Detailed Description
The technical solution of the present invention is further specifically described below by way of specific examples.
In the present invention, all the equipment and materials are commercially available or commonly used in the art, and the methods in the following examples are conventional in the art unless otherwise specified.
Example 1
(1) Adding FeSiAl metal soft magnetic powder into NaAlO2And (NaPO)3)6Heating and stirring the mixed solution at 80 ℃ for 30min until the mixed solution is uniformly mixed, and drying the mixed solution at 100 ℃ to finish insulating coating; the NaAlO is based on the total mass of the FeSiAl metal soft magnetic powder2And (NaPO)3)6The mixed solution of (A) contains 0.1 wt% of NaAlO20.02wt% of (NaPO)3)6And 10 wt% water; NaAlO is added2Dissolving in deionized water and adding (NaPO)3)6Adding, magnetically stirring for 30 minutes to obtain a colorless transparent solution for later use;
(2) after the step (1) of insulating coatingAdding a composite binder into the treated FeSiAl metal soft magnetic powder, fully stirring, and drying at 95 ℃ for 30 min; then adding zinc stearate accounting for 0.5 wt% of the total mass of the FeSiAl metal soft magnetic powder, and performing compression molding under 1500MPa to obtain a composite magnetic powder core blank with the outer diameter of 33.00mm, the inner diameter of 19.90mm and the height of 10.7 mm; the composite binder is composed of 1 wt% of Na2SiO3And 0.01 wt% NaOH;
(3) and (3) carrying out heat treatment on the composite magnetic powder core blank obtained in the step (2) at the temperature of 700 ℃ in vacuum for 45min, cooling and spraying to obtain the all-inorganic high-temperature-resistant composite magnetic powder core.
Example 2
(1) Adding FeSiAl metal soft magnetic powder into NaAlO2And (NaPO)3)6Heating and stirring the mixed solution at 100 ℃, and drying the mixed solution at 90 ℃ to finish insulating coating; the NaAlO is based on the total mass of the FeSiAl metal soft magnetic powder2And (NaPO)3)6The mixed solution of (A) contains 0.2 wt% of NaAlO20.02wt% of (NaPO)3)6And 10 wt% water;
(2) adding a composite binder into the FeSiAl metal soft magnetic powder subjected to the insulation coating treatment in the step (1), fully stirring, keeping the temperature at 90 ℃ for 40min, drying, adding zinc stearate accounting for 0.8 wt% of the total mass of the FeSiAl metal soft magnetic powder and barium stearate accounting for 0.2 wt% of the total mass of the FeSiAl metal soft magnetic powder, and performing compression molding under the pressure of 1800MPa to obtain a composite magnetic powder core blank with the outer diameter of 33.00mm, the inner diameter of 19.90mm and the height of 10.7 mm; the composite binder consists of 2wt% of Na2SiO3And 0.01 wt% NaOH;
(3) and (3) carrying out heat treatment on the composite magnetic powder core blank obtained in the step (2) in nitrogen at the temperature of 600 ℃ for 2h, cooling and spraying to obtain the all-inorganic high-temperature-resistant composite magnetic powder core.
Example 3
(1) Adding FeSiAl metal soft magnetic powder into NaAlO2And (NaPO)3)6Heating and stirring the mixed solution at 90 ℃, and drying the mixed solution at 120 ℃ to finish insulating coating; the NaAlO is based on the total mass of the FeSiAl metal soft magnetic powder2And (NaPO)3)6The mixed solution of (1) includes 0.3wt% NaAlO20.02wt% of (NaPO)3)6And 10 wt% water;
(2) adding a composite binder into the FeSiAl metal soft magnetic powder subjected to the insulation coating treatment in the step (1), fully stirring, keeping the temperature at 100 ℃ for 20min, drying, adding barium stearate accounting for 0.8 wt% of the total mass of the FeSiAl metal soft magnetic powder, and performing compression molding under the pressure of 2000MPa to obtain a composite magnetic powder core blank with the outer diameter of 33.00mm, the inner diameter of 19.90mm and the height of 10.7 mm; the composite binder is composed of 3wt% of Na2SiO3And 0.01 wt% NaOH;
(3) and (3) carrying out heat treatment on the composite magnetic powder core blank obtained in the step (2) in hydrogen at the temperature of 780 ℃ for 0.5h, cooling and spraying to obtain the all-inorganic high-temperature-resistant composite magnetic powder core.
The magnetic powder cores prepared in examples 1 to 3 were subjected to performance tests, and the results are shown in the following table:
the coating process adopted by the invention ensures that the magnetic powder coating layer is thin, uniform and compact, the magnetic conductivity is high, and the loss is greatly reduced. The invention is easy for scale production and has good application prospect.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.